An authentication example for PHP

authn.php

<?php

interface Subject
{
	public function getIdentifier();
	public function getCredential();
}

interface Enforcer
{
	public function evaluate();
}

abstract class Authenticator implements Enforcer
{
	protected $context = [];

	public function __construct($context = array())
	{
		if (!empty($context)) {
			$this->setContext($context);
		}
	}

	public function setContext(array $context)
	{
		$this->context = $context;
	}
	public function getContext($property = null)
	{
		if ($property !== null) {
			return (isset($this->context[$property])) ? $this->context[$property] : null;
		} else {
			return $this->context;
		}
	}
}

class PasswordAuthenticator extends Authenticator
{
	public function evaluate()
	{
		$user = $this->getContext('user');
		$password = $this->getContext('password');

		if ($user === null || $password === null) {
			throw new \Exception('Invalid username or password!');
		}

		// Compare the values
		return password_verify($password, $user->getCredential());
	}
	public function login(Subject $user, $password)
	{
		$this->setContext([
			'user' => $user,
			'password' => $password
		]);
		return $this->evaluate();
	}
}

//--------------------

class User implements Subject
{
	private $properties = [];

	public function __construct($properties)
	{
		$this->properties = $properties;
	}

	public function getIdentifier()
	{
		return $this->properties['username'];
	}
	public function getCredential()
	{
		return $this->properties['password'];
	}
}

$user = new User([
	'username' => 'ccornutt',
	'password' => '$2y$10$qDOrBNv9ZsYE4AmmYOk6BuNIT6uoH2DOahpNep7tS4w3u4NbmCwcG'
]);
echo 'ident: '.$user->getIdentifier()."\n";

$password = 'test1234';

$authn = new PasswordAuthenticator();
$result = $authn->login($user, $password);
echo 'RESULT: '.var_export($result, true)."\n";

echo "\n\n";